1. Field of the Invention
The present invention generally relates to fuse networks, and, more particularly, to providing fault tolerance for fuse networks in integrated circuits.
2. Description of the Related Art
As integrated circuits have become more complicated offering greater functionality, fuse networks have become an integral part of the overall design process. Fuse networks are currently being used for enabling or disabling circuits/circuit blocks, and thereby, providing differing functionality (e.g. customized) without the need to have multiple masks or other redundant circuit processes. In addition, fuse networks are also being used to correct defects in circuits that result from various manufacturing deffiencies (e.g. photolithographis, etch, masking, process).
Obviously, in order to make the fuse(s) useful, some type of circuitry must be used to determine the state of the fuse (e.g. open/close). Fuses are typically blown (opened) via electrical means (e.g. electrical fuse blow) or optical means (e.g., Laser fuse blow). Unfortunately, the techniques used for blowing the fuse can induce enough energy to lead to Electrical OverStress (EOS) or ElectroStatic Discharge (ESD) failure of the circuitry used to read the state of the fuse (xe2x80x9cFuse state circuitryxe2x80x9d). For example, electrical fuse blow can lead to currents which cause failure of the fuse element and the fuse state circuitry at the same time. In further example, laser fuse blow can lead to conversion of optical to thermal energy where the thermal energy can lead to an electrical current, forming a pulsed electrical event propagating into the fuse state circuitry.
It would, therefore, be a distinct advantage to have fuse state circuitry that was protected from both EOS and ESD events. The present invention provides such state circuitry.
The present invention is applicable to fuse networks, and more specifically, to the circuitry that reads the state of the fuse(s) in such networks. The present invention provides ESD, EOS, and CDM protection to the circuitry that reads the state of such fuse(s).